The long-term objective is to develop a serum-free medium that will support the growth and differentiation of hematopoietic cells. Initial research will focus on the development of a serum-free medium that will support the growth and differentiation of RBCs, granulocytes, macrophages, and lymphocytes, with specific attention paid to the purity of each component. Human compounds, only, will be used where biological compounds are found to be necessary. In vitro assays used commonly for hematopoietic cells will be used for this work. It is hoped that this approach will lead to development of a cell-free medium, as well as delineating the role that each component plays in hematopoiesis.